Mammillaria heyderi

Mammillaria heyderi Muehlenpfordt.
Engl.: horsecrippler, little nipple cactus, ball cactus, cream cactus, cream pincushion, flat cream pincushion, pancake pincushion.
Bot. syn.: Mammillaria gummifer Engelm., Mammillaria macdougalii Rose, Mammillaria meiacantha Engelm.